1. Field of the Invention
The present invention relates to an image formation apparatus, such as printer, facsimile or copying machine, which forms an image by employing electrophotography. More particularly, it relates to improvements in a cleaning device which is capable of coming into and out of contact with the front surface of a toner image carrier, and which removes remaining toners adherent on the front surface of the toner image carrier during the contact.
2. Description of the Related Art
In general, an image formation apparatus employing electrophotography includes a photosensitive body which has a photosensitive layer at its outer peripheral surface, a charging device for uniformly charging the outer peripheral surface of the photosensitive body, an exposure device for selectively exposing to light the outer peripheral surface having been uniformly charged by the charging device, thereby to form an electrostatic latent image, a developing device for giving toners being developing agents, to the electrostatic latent image formed by the exposure device, thereby to turn the latent image into a visible image (toner images), a transfer device for transferring the toner images developed by the developing device, onto a sheet of paper or the like recording medium being a subject for transfer, and a cleaning device for removing the toners remaining on the front surface of the photosensitive body after the transfer.
Known as the transfer device is one having a toner image carrier (for example, intermediate transfer medium) onto which the toner images formed on the photosensitive body are transferred (primarily transferred), which carries the transferred toner images thereon, and which transfers (secondarily transfers) the toner images onto the sheet of paper or the like recording medium being the subject for transfer. The intermediate transfer medium (toner image carrier) is also furnished with a cleaning device.
Usually, the cleaning device of the photosensitive body need not have a construction in which it is brought into and out of contact with the photosensitive body. Since, however, the intermediate transfer medium (toner image carrier) collectively transfers the toner images in, for example, a plurality of colors as have been superimposed, onto the subject for transfer (the sheet of paper or the like recording medium), the cleaning device needs to be brought out of contact with the intermediate transfer medium during the superimposition operation of the toner images, and to be brought into contact after the collective transfer.
In such an image formation apparatus, when the cleaning device has come out of contact with the toner image carrier, the toners adhering to the cleaning device scatter and float within the image formation apparatus, thereby to incur various problems that the toners adhere to the intermediate transfer medium or the photosensitive body to degrade a picture quality, that the toners pollute the interior of the apparatus, and so forth.
In this regard, there has heretofore been proposed an image formation apparatus which is furnished with a shutoff mechanism for shutting off a toner outflow port when the cleaning device has come out of contact with the front surface of the toner image carrier (refer to, for example, JP-A-2003-295722).
The related art technique has had the problem that, even when the shutoff mechanism is quickly actuated, the toners scatter yet. Also, it has had the problem that, since the shutoff mechanism needs to be disposed, the structure of the apparatus becomes complicated.